A Big, Empty Castle

The main difference between video games and tabletop games (such as Dungeons and Dragons) is the concept of player freedom. Even the most open-world video games have constraints somewhere in them. Grand Theft Auto V's map has to end eventually, right? Whereas D&D can conceivably go on forever, assuming the Dungeon Master has enough brain and willpower to do so.

A few years ago, I thought this automatically meant that Dungeons and Dragons was better, at least from a conceptual standpoint. After all, what's better than infinite freedom? Nothing! When I first discovered tabletop RPGs, that fact impressed me to no end. I believed that if I were stuck on a desert island, I would only need my imagination and a few people to share it, and I'd be happy. Since then, my thinking has changed a bit, and probably not for the reasons you're thinking.

Player freedom is one thing, but I've really learned the importance of constraints. Here are two contrasting examples:

Example 1:
Players in D&D are rewarded a vast castle. Inside, they can possibly hire servants, craftsmen and hundreds of other cool things. Despite this, the players never really use it. They move on, uninterested. This is simply another huge asset, like a pile of gold, that they have collected.

Example 2:
Players in a video game (let's say Skyrim) are given a house as a quest reward. They can hire a servant, upgrade various stations in the house (like a blacksmith or alchemy table) and decorate the inside. The player returns to this house frequently to take advantage of its services.

So what's the difference here? After some careful consideration, I've thought of a few things.

Difference 1: Explicit Definition of Value
In Skyrim, the value of a player's house is made evident immediately. The game tells you "here is a single location for every crafting table in the game, and a place to store your stuff." In D&D, you're given a large chunk of undefined space to play in.
To put it in practical terms, if I gave you a big empty warehouse and said "do whatever you want," you probably would, at least initially, struggle to think of what to do. Conversely, if I gave you a small room with a trampoline in it, you'd immediately know what to do. It's not that the trampoline is better than a 20,000 square foot warehouse, it's that its function is immediately clear.

Nice and empty.

Difference 2: Player Creativity
In this world of video games, smart phones and tablets, people are very comfortable with constraints. Most people don't want infinite experiences, they wants Angry Birds. Give them something that's easy to understand and quick to play. The exception would be building games like Minecraft, where players really can do practically anything they want. But even Minecraft has constraints; you can't build infinitely high, or dig infinitely low. The experience is defined from the moment you punch your first tree.

People who have never played Dungeons and Dragons might struggled to create in the same way they might create in Minecraft. You're not building a castle one block at a time, you're creating vast concepts in just a few sentences. D&D is a game mainly about talking, and although neither Minecraft nor D&D has tactile feedback for a player, you can see what you're doing in Minecraft, whereas you have to imagine things in D&D.

If I said "build me a castle" in Minecraft, I know many people who could and would immediately build something very impressive, down to the smallest detail.

If the same thing was asked of D&D, people wouldn't start by describing exact length, width and height (well, maybe some people would). They would describe the surrounding lands, the Kingdom, and then hone in on how the castle looked in terms of a mood or tone.

"My castle shines like a beacon on the hill overlooking Barton Cliff. It's made of white stone, and the people inside are suffering under the reign of King Odin."

Difference 3: Explanation of Constraints
Unless you're a writer, it's difficult for Dungeon Masters to give high detail all the time. It doesn't matter how beautiful the opening paragraph is; as soon as a player asks to find a tavern, the GM has to quickly make up something. "It's called the Singing Shrew, and it stinks like old beer," is about as much description as you're gonna get.

It's a sketch more than anything.

Very quickly, a world in D&D can feel paper-thin as you travel into buildings that don't exist, talk to people who weren't defined a minute ago, and finding bonkers solutions to problems you created for yourself.
In many ways, the lack of constraints can be detrimental.

Let's look at Skyrim again. You know that if you travel into a building, there will be walls that you can't climb. There will be people there who you probably shouldn't kill, and objects you can steal. Everything is clearly and explicitly defined. It's a system of constraints that's immediately understandable and functional.

For a time, I was interested in adapting the Fallout universe into a tabletop RPG. The more I thought about it, the more I realized that what I like about the Fallout games isn't remotely the same as what I like to do in TTRPGs. For me, Fallout is all about being alone in a vast world, exploring the unknown and methodically sifting through piles of trash for small prizes.

It's probably not very enjoyable for other people to watch.

When I play D&D, what I enjoy most is making a character with a compelling story, interacting with the other players both in and out of the game, and solving problems in creative ways. I adore the discovery of the unknown, but not in the same way as Fallout. I know that in Fallout, every object was intentionally placed by a designer. In D&D, many, many encounters and rewards are randomized in some way, simply because it's really, really hard for a GM to both run a coherent game and track all of the minutiae behind the scenes.

Is this fixable?
I think that depending on the kind of game you want to run, the GM needs to be more intentional and explicit with the information given. You really shouldn't say, "here's a huge castle, have fun." You should say, here's a castle, and here's a sheet of paper describing how you can use it and what you can get from it. It doesn't have to be a detailed simulation of castle economics from the middle ages, but the GM should do something to make the world seem more understandable and clear. Otherwise it's just a sandbox with toys strewn hither and thither.

It call comes back to human psychology and whether or not a person feels creative in the moment. I've played games of D&D with people who would jump on that castle and start using it in ways that I never imagined. In this case, a list of constraints would limit that person and their creativity. It really all comes down to the group and the individual.